1. Field of the Invention
This invention relates to communication networks, more particularly it relates to security within these networks.
2. Description of the Prior Art
One of the most significant recent developments in wireless technologies is the emergence of wireless personal area networking. Wireless personal area networks WPANs™, use radio frequencies to transmit both voice and data) and are specified by standards such as IEEE standard 802.15 or 802.3 from the Institute of Electrical and Electronics Engineers Standards Association (IEEE-SA), among other specifications. The 802.15 specification is ideal for linking notebook computers, mobile phones, personal digital assistants (PDAs), digital cameras, and other handheld devices to do business at home, on the road, or in the office.
These wireless networks are formed by a number of devices joining and leaving the network in an ad hoc manner, hence such networks are known as ad hoc networks or piconets. Thus, the set of devices connected to the ad hoc network any given time may fluctuate, and so the topology of the network is dynamic. It is desirable to control access to the network and to provide a mechanism for establishing and maintaining security. Traditionally, security is established using a central device or a piconet controller (PNC) which controls access and distributes keys within the network. A drawback of this scheme is that each member of the network is required to trust the PNC.
Admission to the piconet is based on the outcome of the following protocols between the prospective joining device and the PNC of the piconet. The joining device and the PNC engage in a mutual entity authentication protocol based on pubic key or symmetric key techniques. The true device identity of both the joining device and the PNC is determined using this protocol. A link key can also be derived based on the authentic keys of both parties. Another protocol involves using authorization techniques between both devices, based on access control lists (ACLs). The Access Control Lists may be dynamically updated, similar to PDA functionality, where a determination is made whether an entity is added or removed from the ACL at entry. This determination may be made by an operator, such as a human operator. For devices that lack a user interface, this update mechanism may be invoked by an open enrollment period followed by a lock-up step, for example, which may be confirmed by a button push or be a simple re-set of the whole list. This may be performed by actuating a re-set or re-initialize button on the device.
Thus devices in the piconet fully depend on information provided by the PNC regarding which devices have been admitted to the piconet, since admission is based on communication between the PNC and a joining device only. If however an improper list of devices, DeviceList, in the piconet has been distributed by the PNC, either by error or maliciously, the security of the network is jeopardised. Each device has a short hand address, such as a local 8-bit ID, and a long hand address, such as a global 48-bit device ID. For example, in a piconet in which since all devices share a common broadcast key, the list of admitted devices to the piconet is L:=(local 8-bit device ID, global 48-bit device ID), then the failure to obtain the complete and authentic list of admitted devices has the following consequences:
‘Fly on the wall’ scenario:
If a device obtains an incomplete list: L′⊂(L′≠L) of admitted devices, all devices in the complementary set L\L′ are ‘invisible’ to the device. Hence, the device might mistakenly think it is sharing secured information only with devices from the list L′, whereas actually it is unknowingly sharing with other devices of the set L as well. This obviously violates sound security practice.
‘Switchboard’ scenario'.
If the binding between the local device ID and the global device ID is incorrectly received, for example if 2 entries are interchanged, a device might direct information to the improper device and so compromise the intended security. This property also holds in other settings where a key-generating party does not share complete and authentic information on the composition of the key-sharing group itself with the other members of this group. Therefore, these scenarios present a security model in which there is complete trust or a security model in which a device trusts no other device, however a hybrid model of these two models is possible.
Accordingly it is an object of the present invention to mitigate or obviate at least one of above-mentioned disadvantages.